• In a medium stainless-steel bowl, whisk together the egg yolks, sugar, lemon juice, lemon zest, butter and salt.
• Put 1 inch / 2.5cm of water in the bottom of a double boiler or a medium saucepan and bring to a gentle simmer over medium heat. Place the bowl with the lemon mixture over the simmering water.
• Using a rubber spatula, stir the mixture constantly, making sure to clean the sides of the bowl as you go, until the lemon curd begins to thicken, about 10 minutes; it will be the consistency of smooth pudding.
• If there are any lumps in the curd, strain it through a fine-mesh sieve into a shallow container and cover with plastic wrap, pressed directly onto the surface, to prevent a skin from forming.
• In a large bowl, add enough ice cubes and cold water to create a bath for the container to sit in without the water breaching the sides.
• Set the container in the ice bath or place in the freezer until chilled, about 15 minutes, then transfer to the fridge for up to 5 days.

Variation: Citrus Curd

• Try the curd with lime, grapefruit, or passionfruit for a different taste sensation. Prepare as directed but swap out the lemon for another typeof juice and zest. Or try an orange-lemon curd, using 1/4 cup / 60ml orange juice and 1/4 cup / 60ml lemon juice, plus the zest of 1/2 orange. (Oranges on their own will be too sweet.)